TV: Previews

The oddity of `Underworld' is that it is a cartoon which keeps turning photographic, so that what you have taken for a comic caricature of evil will suddenly reveal a patch of shocking forensic detail

It's an unusual comedy which shows you photographs of a charred Iraqi soldier welded to the metalwork of his burnt-out truck, or of a famine-stricken child, crouched in the dust while a vulture waits patiently in the background. Such sights are liable to wipe smiles off faces, and once wiped there may be no easy way to replace them. In Underworld (Channel 4), which is a most unusual comedy, the pictures in question were displayed during a tour of a neurological unit doing research into the origins of psychopathy - Kevin McNally, who plays a deranged gangster called Jezzard, listened politely to the doctor's explanation and stared intently at the images, like someone trying to solve a puzzle. Something disturbing was hidden in there somewhere, but he couldn't for the life of him work out what it was.

That particular moment was emblematic, because the oddity of Underworld is that it is a cartoon which keeps turning photographic, so that what you have taken for a comic caricature of evil will suddenly reveal a patch of shocking forensic detail. Early in the series, for example, Jezzard's brutality was established in the middle of one of those silky passages of threat that are so familiar from the gangster genre. "Do you know how many bones there are in the human face?" he gently asks a frightened woman, and then answers her by parading a badly beaten girl, her face almost unrecognisable beneath a mask of cuts and swelling. That wasn't funny at all, indeed it pushed the definition of black humour very close to the point where it turns nauseous. But it wasn't simple titillation - Andy Hamilton (whose comedy credentials have already been firmly established in Drop the Dead Donkey and some excellent one-off satires) has larger ambitions here. He is interested, among other things, in the way that genre television routinely plays down the consequences of violence. In one scene last night, a convoy of heavily armed gangsters happens across a film crew shooting some trashy thriller - all shotguns and shouting. As the scene unwinds, its cliched urgencies are interrupted by Frank, who gives the director an unwanted tutorial in the physiological effects of extreme terror by sticking a real gun to his head: "When you shoot someone, you actually start a lot of stories," he hisses, outlining the cascade of misery that follows a killing. He then continues on his way to blow Jezzard's house to pieces around his ears - a jaunty catastrophe which is played as black farce.

This oscillation between flippancy and philosophy doesn't always work; there are occasions when the solemnity hasn't been entirely incorporated into the story (the sub-plot about the beloved aunt dying of cancer seems to be making a point about the way in which life can be as unappeasably cruel as any hit-man, but it still seems a bit tacked on). When it does work, though, it's because Hamilton has taken care to build some genuine feelings into his drama. There are nice running jokes (I like the thick henchman with a weakness for doing impressions, a man who is forever deflating his boss's carefully cultivated mood of menace by chipping in with a bit of Jimmy Savile or Frank Bruno) and the essential comic architecture - innocents out of their depth - is already well proven. But less familiar are the interludes in which ancient family grievances slowly come to the surface. There are gags here too, of course - "I haven't been so scared since we had to tell Mum we painted that swastika on the tortoise" says Susan Woolridge at one point - but the line isn't simply an absurd comparison; it fills out the sense of a past life that has laid the foundations for the bickering, intimate dependence these characters have on each other. Even the gangsters have a private life - whether Jezzard's psychotic anxiety to father a child, or Frank Middlemass's repentant self-improvement (he reads books and dreams of endowing a college for poor children). Underworld is worth watching, not for the twists of its thriller plot but for the unpredictable emotions that have been trapped within those tangles.